xfs: add CRC checks to the AGFL

Add CRC checks, location information and a magic number to the AGFL.
Previously the AGFL was just a block containing nothing but the
free block pointers.  The new AGFL has a real header with the usual
boilerplate instead, so that we can verify it's not corrupted and
written into the right place.

[dchinner@redhat.com] Added LSN field, reworked significantly to fit
into new verifier structure and growfs structure, enabled full
verifier functionality now there is a header to verify and we can
guarantee an initialised AGFL.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Ben Myers <bpm@sgi.com>
Signed-off-by: Ben Myers <bpm@sgi.com>

1 files changed, 78 insertions, 41 deletions

diff --git a/fs/xfs/xfs_alloc.c b/fs/xfs/xfs_alloc.c
index c34f799aa92e..40d3d576f473 100644
--- a/fs/xfs/xfs_alloc.c
+++ b/fs/xfs/xfs_alloc.c
@@ -432,53 +432,84 @@ xfs_alloc_fixup_trees(
 	return 0;
 }
 
-static void
+static bool
 xfs_agfl_verify(
 	struct xfs_buf	*bp)
 {
-#ifdef WHEN_CRCS_COME_ALONG
-	/*
-	 * we cannot actually do any verification of the AGFL because mkfs does
-	 * not initialise the AGFL to zero or NULL. Hence the only valid part of
-	 * the AGFL is what the AGF says is active. We can't get to the AGF, so
-	 * we can't verify just those entries are valid.
-	 *
-	 * This problem goes away when the CRC format change comes along as that
-	 * requires the AGFL to be initialised by mkfs. At that point, we can
-	 * verify the blocks in the agfl -active or not- lie within the bounds
-	 * of the AG. Until then, just leave this check ifdef'd out.
-	 */
 	struct xfs_mount *mp = bp->b_target->bt_mount;
 	struct xfs_agfl	*agfl = XFS_BUF_TO_AGFL(bp);
-	int		agfl_ok = 1;
-
 	int		i;
 
+	if (!uuid_equal(&agfl->agfl_uuid, &mp->m_sb.sb_uuid))
+		return false;
+	if (be32_to_cpu(agfl->agfl_magicnum) != XFS_AGFL_MAGIC)
+		return false;
+	/*
+	 * during growfs operations, the perag is not fully initialised,
+	 * so we can't use it for any useful checking. growfs ensures we can't
+	 * use it by using uncached buffers that don't have the perag attached
+	 * so we can detect and avoid this problem.
+	 */
+	if (bp->b_pag && be32_to_cpu(agfl->agfl_seqno) != bp->b_pag->pag_agno)
+		return false;
+
 	for (i = 0; i < XFS_AGFL_SIZE(mp); i++) {
-		if (be32_to_cpu(agfl->agfl_bno[i]) == NULLAGBLOCK ||
+		if (be32_to_cpu(agfl->agfl_bno[i]) != NULLAGBLOCK &&
 		    be32_to_cpu(agfl->agfl_bno[i]) >= mp->m_sb.sb_agblocks)
-			agfl_ok = 0;
+			return false;
 	}
+	return true;
+}
+
+static void
+xfs_agfl_read_verify(
+	struct xfs_buf	*bp)
+{
+	struct xfs_mount *mp = bp->b_target->bt_mount;
+	int		agfl_ok = 1;
+
+	/*
+	 * There is no verification of non-crc AGFLs because mkfs does not
+	 * initialise the AGFL to zero or NULL. Hence the only valid part of the
+	 * AGFL is what the AGF says is active. We can't get to the AGF, so we
+	 * can't verify just those entries are valid.
+	 */
+	if (!xfs_sb_version_hascrc(&mp->m_sb))
+		return;
+
+	agfl_ok = xfs_verify_cksum(bp->b_addr, BBTOB(bp->b_length),
+				   offsetof(struct xfs_agfl, agfl_crc));
+
+	agfl_ok = agfl_ok && xfs_agfl_verify(bp);
 
 	if (!agfl_ok) {
-		XFS_CORRUPTION_ERROR(__func__, XFS_ERRLEVEL_LOW, mp, agfl);
+		XFS_CORRUPTION_ERROR(__func__, XFS_ERRLEVEL_LOW, mp, bp->b_addr);
 		xfs_buf_ioerror(bp, EFSCORRUPTED);
 	}
-#endif
 }
 
 static void
 xfs_agfl_write_verify(
 	struct xfs_buf	*bp)
 {
-	xfs_agfl_verify(bp);
-}
+	struct xfs_mount *mp = bp->b_target->bt_mount;
+	struct xfs_buf_log_item	*bip = bp->b_fspriv;
 
-static void
-xfs_agfl_read_verify(
-	struct xfs_buf	*bp)
-{
-	xfs_agfl_verify(bp);
+	/* no verification of non-crc AGFLs */
+	if (!xfs_sb_version_hascrc(&mp->m_sb))
+		return;
+
+	if (!xfs_agfl_verify(bp)) {
+		XFS_CORRUPTION_ERROR(__func__, XFS_ERRLEVEL_LOW, mp, bp->b_addr);
+		xfs_buf_ioerror(bp, EFSCORRUPTED);
+		return;
+	}
+
+	if (bip)
+		XFS_BUF_TO_AGFL(bp)->agfl_lsn = cpu_to_be64(bip->bli_item.li_lsn);
+
+	xfs_update_cksum(bp->b_addr, BBTOB(bp->b_length),
+			 offsetof(struct xfs_agfl, agfl_crc));
 }
 
 const struct xfs_buf_ops xfs_agfl_buf_ops = {
@@ -1984,18 +2015,18 @@ xfs_alloc_get_freelist(
 	int		btreeblk) /* destination is a AGF btree */
 {
 	xfs_agf_t	*agf;	/* a.g. freespace structure */
-	xfs_agfl_t	*agfl;	/* a.g. freelist structure */
 	xfs_buf_t	*agflbp;/* buffer for a.g. freelist structure */
 	xfs_agblock_t	bno;	/* block number returned */
+	__be32		*agfl_bno;
 	int		error;
 	int		logflags;
-	xfs_mount_t	*mp;	/* mount structure */
+	xfs_mount_t	*mp = tp->t_mountp;
 	xfs_perag_t	*pag;	/* per allocation group data */
 
-	agf = XFS_BUF_TO_AGF(agbp);
 	/*
 	 * Freelist is empty, give up.
 	 */
+	agf = XFS_BUF_TO_AGF(agbp);
 	if (!agf->agf_flcount) {
 		*bnop = NULLAGBLOCK;
 		return 0;
@@ -2003,15 +2034,17 @@ xfs_alloc_get_freelist(
 	/*
 	 * Read the array of free blocks.
 	 */
-	mp = tp->t_mountp;
-	if ((error = xfs_alloc_read_agfl(mp, tp,
-			be32_to_cpu(agf->agf_seqno), &agflbp)))
+	error = xfs_alloc_read_agfl(mp, tp, be32_to_cpu(agf->agf_seqno),
+				    &agflbp);
+	if (error)
 		return error;
-	agfl = XFS_BUF_TO_AGFL(agflbp);
+
+
 	/*
 	 * Get the block number and update the data structures.
 	 */
-	bno = be32_to_cpu(agfl->agfl_bno[be32_to_cpu(agf->agf_flfirst)]);
+	agfl_bno = XFS_BUF_TO_AGFL_BNO(mp, agflbp);
+	bno = be32_to_cpu(agfl_bno[be32_to_cpu(agf->agf_flfirst)]);
 	be32_add_cpu(&agf->agf_flfirst, 1);
 	xfs_trans_brelse(tp, agflbp);
 	if (be32_to_cpu(agf->agf_flfirst) == XFS_AGFL_SIZE(mp))
@@ -2104,12 +2137,13 @@ xfs_alloc_put_freelist(
 	int			btreeblk) /* block came from a AGF btree */
 {
 	xfs_agf_t		*agf;	/* a.g. freespace structure */
-	xfs_agfl_t		*agfl;	/* a.g. free block array */
 	__be32			*blockp;/* pointer to array entry */
 	int			error;
 	int			logflags;
 	xfs_mount_t		*mp;	/* mount structure */
 	xfs_perag_t		*pag;	/* per allocation group data */
+	__be32			*agfl_bno;
+	int			startoff;
 
 	agf = XFS_BUF_TO_AGF(agbp);
 	mp = tp->t_mountp;
@@ -2117,7 +2151,6 @@ xfs_alloc_put_freelist(
 	if (!agflbp && (error = xfs_alloc_read_agfl(mp, tp,
 			be32_to_cpu(agf->agf_seqno), &agflbp)))
 		return error;
-	agfl = XFS_BUF_TO_AGFL(agflbp);
 	be32_add_cpu(&agf->agf_fllast, 1);
 	if (be32_to_cpu(agf->agf_fllast) == XFS_AGFL_SIZE(mp))
 		agf->agf_fllast = 0;
@@ -2138,13 +2171,17 @@ xfs_alloc_put_freelist(
 	xfs_alloc_log_agf(tp, agbp, logflags);
 
 	ASSERT(be32_to_cpu(agf->agf_flcount) <= XFS_AGFL_SIZE(mp));
-	blockp = &agfl->agfl_bno[be32_to_cpu(agf->agf_fllast)];
+
+	agfl_bno = XFS_BUF_TO_AGFL_BNO(mp, agflbp);
+	blockp = &agfl_bno[be32_to_cpu(agf->agf_fllast)];
 	*blockp = cpu_to_be32(bno);
+	startoff = (char *)blockp - (char *)agflbp->b_addr;
+
 	xfs_alloc_log_agf(tp, agbp, logflags);
-	xfs_trans_log_buf(tp, agflbp,
-		(int)((xfs_caddr_t)blockp - (xfs_caddr_t)agfl),
-		(int)((xfs_caddr_t)blockp - (xfs_caddr_t)agfl +
-			sizeof(xfs_agblock_t) - 1));
+
+	xfs_trans_buf_set_type(tp, agflbp, XFS_BLF_AGFL_BUF);
+	xfs_trans_log_buf(tp, agflbp, startoff,
+			  startoff + sizeof(xfs_agblock_t) - 1);
 	return 0;
 }